mp3-youtube does not store any data whether it's private or public (We have no database at all).
We do use some external scripts or libraries that might set a Cookie, but these are from trustfull partners or big companies and it's crutial for the service to continue working.
The requests you sent us are anonymous and we do free our log requests each week.
We take to right to store any sucpicious request that try to abuse our service so that we can know the issuer.